1. Field of the Invention
The present invention relates generally to a device for detecting thermal differentials emanating from a body and for transforming such differentials to a visible representation for thermographic recording. More particularly, the invention relates to a combination of an elastomeric film containing temperature responsive cholesteric liquid crystals to locate and to convert surface areas of temperature gradients to color patterns and an imaging system for photographing such patterns.
2. Description of the Prior Art
Medical literature is increasingly demonstrating how thermal sensing devices and materials can aid in the diagnosis of disorders when correlated with an individual's clinical history, physical examination and other laboratory tests and in the study of physiological reactions to pharmodynamic substances such as immunological, hormonal and vasomotor drugs. The field of study involving the use of thermal sensing devices and materials, or thermography, may be defined as a process for detecting abnormal or diseased underlying conditions of an organism which produce temperature changes and for transforming these resulting thermal differentials emanating from such disorders or lesions to a visible display for photographic recording and analysis.
Early work, which was conducted to determine a methodology whereby elevated or so-called "hot areas", created by an infusion of an extraordinary number of blood vessels, may be indicative of an underlying disorder such as a neoplast, involved the remote sensing of the infrared radiation emitted from a scanned area. However, the sensing equipment developed to detect the emitted radiation produced thermographic outputs that erroneously indicated positive readings. Because of the frequency of such false readings, the lack of agreement as to the results obtained made the procedure unacceptable. Furthermore, such electronic infrared sensing equipment is very expensive and requires the use of skilled personnel.
Independent of the work in the area of electronic infrared thermography since 1968 there has been a substantial effort in laboratories throughout the world in developing display devices and temperature sensors using liquid crystals. These compounds, which conventionally are divided into three classes, namely, smetic, nematic, and cholesteric, possess one or more mesomorphic phases, intermediate between their solid crystal form and their isotropic form. In response to subtle temperature changes the colorless isotropic form of cholesteric liquid crystals, due to their unique molecular structure, undergoes an optical transformation as it passes through the highly colored mesomorphic phase.
As an alternative to electronic infrared thermography researchers directed cholesteric thermotropism to the problem of visually viewing invisible radiation emitted from an object which falls within the infrared portion of the electromagnetic spectrum. Early disclosures such as contained in U.S. Pat. No. 3,533,399 revealed a procedure whereby a first layer most commonly comprising a black pigment and a second layer of cholesteric substances were applied to the skin area under investigation to produce visible thermal patterns that could be photographed. The impracticality of the time consuming procedure for mass screening and routine examination, the nonreuseability of materials, the uneasiness of patients negatived acceptance of the procedure.
In order to overcome the disadvantages inherent in the procedure of coating body areas with temperature responsive materials and their subsequent removal, nonuniformity of coatings, nonrecovery of materials, thermometric devices comprising liquid crystal materials that scan a surface area to produce thermograms containing information pertaining to temperature variations over the scanned areas were disclosed. U.S. Pat. No. 3,847,139 is typical of such disclosures in which body contour garments, such as brassieres, incorporating temperature responsive substances produce thermal patterns that are observed and photographically recorded for comparative analysis. Due to differences of sizes and shapes of women's breasts, such garments are not satisfactory because they lack the conformability necessary to uniformally contact all of the scanned areas being investigated.
Disclosed as a process (particularly for the detection of mammary anomalies) that overcomes the inherent disadvantages of coating body areas with thermosensitive materials, or the use of flexible supports disposed against the surface under examination, or the utilization of supports called "thermosensitive pellicles with liquid crystals", U.S. Pat. No. 4,060,654 teaches the use of a composite lamellar pellicle for producing photographable thermographic patterns by using liquid crystal materials applied to an inner sheet and sandwiched between two outer sheets which are enframed to preserve the planar shape. By using a temperature responsive series of pellicles containing different admixtures of liquid crystal materials, the practitioner can determine the thermal topography of a body regardless of the ambient temperature. However, because the pellicles are mounted in rigid rectangular frames, the device is conformability restricted in that it cannot be used on curved surface areas. Furthermore, lamellar pellicle thermography and the interpretation of thermograms is limited to clinical research facilities, hospitals, and doctors offices; being unsuited for direct use by the patient in her home.
In order to overcome the conformability limitations of thermoresponsive fabric brassieres and lamellar pellicles, a brassiere-like apparatus, as disclosed in U.S. Pat. No. 4,135,497, provides liquid crystals interposed between flexible sheets to form a composite film. Conformance of the film to the contours of the body is attained by evacuation of air between the film secured in place by means of a pair of elastic straps encircling the women's chest and the body surface. The heat emitted by tissues of the various regions are transformed by the film into color patterns or thermograms which may be photographically recorded. However, the excessive time consuming special techniques to ensure body conformity tends to obviate the apparatus as a practical procedure for mass screenings and routine examinations, apparatus bulk and complexity preclude its use to the more sophisticated medical facilities, and narrow thermoresponsive range composite film limit the application of a film to a particular tissue region.